1. Field of the Invention
The present invention relates to an image pickup apparatus capable selecting one of a plurality of different aspect ratios to record image data.
2. Description of Related Art
An image pickup apparatus capable of recording image data having different aspect ratios is disclosed in JP 6(1994)-086114A, for example. The image pickup apparatus disclosed in JP 6(1994)-086114A is an image pickup apparatus to which an optical system including an anamorphic lens for converting the aspect ratio of captured images can be mounted, wherein, when image-taking is performed after mounting the optical system, the parameters of the circuit involved in acquiring image pick-up signals (image signals) are corrected according to the aspect ratio transfer characteristics of the optical system. This provides an image pickup apparatus capable of taking images having various aspect ratios, and always maintaining a certain level of controlling capability and image quality at the time of image-taking for images of all aspect ratios
Although not described in a published document, the applicant recognizes techniques shown in FIG. 15 and FIG. 16 as related arts. FIG. 15 is a diagram showing the relationship among use regions on a solid-state imaging device in an image pickup apparatus of Related Art 1. FIG. 16 is a diagram schematically showing the relationship between use regions on a solid-state imaging device in an image pickup apparatus of Related Art 2. Here, a “use region” means a pixel area on a solid-state imaging device for generating image data that is used when generating image data for recording.
In FIG. 15, use region E101 is the use region in a 16:9 mode, and its height is represented by V101. Use region E102 is the use region in a 3:2 mode, and its height is represented by V102. Use region E103 is a use region in a 4:3 mode, and its height is represented by V103. The relationship among V101 to V103 is as follows:V101<V102<V103  (Formula 101)In addition, the widths of the use regions are all H100 and equal. That is, according to Related Art 1, the widths of all the use regions having aspect ratios that are different from one another are set to be equal, and their heights are set to be different from one another.
In FIG. 16, use region E111 is the use region in the 16:9 mode, and its width is represented by H111. Use region E112 is the use region in the 3:2 mode, and its width is represented by H112. Use region E113 is the use region in the 4:3 mode, and its width is represented by H113. The relationship among H111 to H113 is as follows:H113<H112<H111  (Formula 102)In addition, the widths of the use regions are all V110 and equal. That is, according to Related Art 2, the heights of all the regions having aspect ratios that are different from one another are set to be equal, and the widths thereof are set to be different from one another.
As described above, according to Related Arts 1 and 2, the image data corresponding respectively to the aspect ratios are extracted from the solid-state imaging device and subjected to image processing, so that it is possible to obtain image data for recording having different aspect ratios relatively easily.
However, although the image pickup apparatus described in JP 6(1994)-086114A has an effect of always maintaining a certain level of control capability and image quality at the time of image-taking for images of all aspect ratios, this requires mounting of an anamorphic lens. Accordingly, the image pickup apparatus described in JP 6(1994)-086114A has a problem in that it requires a complicated operation, and also in that it has a cost disadvantage due to the large number of required components.
Furthermore, with the image pickup apparatuses of Related Arts 1 and 2, there will be differences in size among data constituting images having different aspect ratios. That is, according to Related Art 1, the size of the image data output from the solid-state imaging device is largest when the aspect ratio is 4:3, and smallest when the aspect ratio is 16:9. The reason that there are differences in data size in this way is that the numbers of pixels in the use regions (E101 to E103) differ among the aspect ratios. This is also true in Related Art 2. This means that the number of pixels of the image data read from the solid-state imaging device differs for each aspect ratio, so that when the same image processing is performed for image data having various aspect ratios, the size of the image data for recording varies depending on the aspect ratio. On the other hand, when different image processes are performed for image data having various aspect ratios to make their image data sizes uniform, the image quality of the image data for recording varies depending on the aspect ratio. Therefore, the image pickup apparatuses according to Related Arts 1 and 2 have a problem in that when images have different aspect ratios, there will be differences in size among the data constituting the images, and hence the sizes or qualities of the images for recording vary.
Furthermore, with the image pickup apparatuses of Related Arts 1 and 2, the diagonal angle of view greatly varies among images having various aspect ratios. Therefore, it is necessary to design the size of the effective image circle of the lens so as to be suitable for images having a large diagonal angle of view, so that the effective image circle of the lens will be unnecessarily large for images having a small diagonal angle of view. This poses a problem that the effective image circle of the lens cannot be utilized efficiently for images having a small diagonal angle of view. This problem tends to occur especially in image pickup apparatuses provided with a solid-state imaging device having a rectangular image-taking region, such as a CCD image sensor or a MOS image sensor. In contrast, this problem tends not to occur in image pickup apparatuses provided with a camera tube having a circular image-taking region.